can read, inefficiently

It's inefficient because it's somewhat unusual, and because when we read our brains are trained to recognise larger patterns instead of just single characters, so of course if you've spent all your like reading 東京 instead of とうきょう, the first would be recognisable much more quickly.

But that's true as much of modern Japanese as it was of Korean before they dropped Chinese characters, or of Chinese before the simplification of Hanzi.

Eventually, people would just get used to a new way of writing things and be able to absorb that quickly and efficiently.

Nah, kana take up way too much space, and with no spaces in the language that makes parsing kana only text a lot slower than kanji.

On top of that, the language itself is phonetically very simple, so if you didn't have kanji there would be way too much ambiguity in written text, which is already very differen from spoken Japanese.

Now, if Japanese invented a new Korean style alphabet that combines sounds into a single character, and introduced spaces to the language then I could see it working, but I don't think most people would want that.

Japanese children are able to cope with all-hiraganas only because the text they read are so short and simple, accompanied by pictures. No other kind of books are written in all hiraganas, meaning that no person on earth has the required training. Nor do I think it's practical because there are likely to be tons of disambiguation problems with hiragana text.

Also, as I said, what worked for Korea centuries ago won't work for modern day Japan. Hangul was developed in an entirely different era where most people was illiterate, and the means for scaling education was non-existent by today's standards. It therefore made sense to reduce the number of letters in the alphabet. However, in modern age Japan, you'll be hard pressed to find a healthy person who can't read or write. There's no reason nor desire to switch to hiraganas only, and every reason otherwise. Changing a language is probably a terrible idea if there's no documented instance of native speakers actually wanting the change.

> Nor do I think it's practical because there are likely to be tons of disambiguation problems with hiragana text.

Humans are good at disambiguating in context. Those ambiguities can arise in spoken language too (minus those that are differentiated by pitch accent, but that still leaves enough room for homonyms).

> Changing a language is probably a terrible idea if there's no documented instance of native speakers actually wanting the change.

I agree but that has something to do with sociological reasons. I wasn't advocating for changing Japanese.

As late as the Edo period, there were entire genres of literature that were written almost entirely in Kana: https://en.m.wikipedia.org/wiki/Kanaz%C5%8Dshi

Clearly, people were able to read that.